For the sole purpose of determining whether a member has completed the required 24 years of creditable service referred to in this subsection (b) or the date on which he would have completed such period of creditable service if he had remained in membership service, in the case of a member of the Teachers' and State Employees' Retirement System who became a member of this Retirement System under circumstances described in G.S. 135-28.1, and who at the time of his retirement hereunder is in service and has retained his membership in the Teachers' and State Employees' Retirement System as provided for in G.S. 135-28.1, his creditable service shall be taken as the sum of his creditable service hereunder plus the amount of creditable service remaining to his credit in such other system as provided for in G.S. 135-28.1.
N.C. Gen. Stat. § 135-58